Luffing jib for construction crane

Abstract

A massive crane luffing jib is held and loaded under compression atop the main crane boom such as a hydraulically extensible and retractable telescopic boom whose sections may be locked for safety. The luffing jib is pivoted to an adapter atop the boom to enable swinging the jib to a stowed position close to and along the front side of the boom. First, second and third masts are pivotally attached to the jib base section. The second and third masts are connected by foldable tension links. An upper foldable ladder in the pendant line between the point of the jib and bridle assembly forms a hard connection between the first and second masts. A lower foldable ladder including a gooseneck forms a hard connection between the second and third masts following automatic coupling of the gooseneck with the third mast after the tension link becomes fully extended. A safety backstop or stay connected between the luffing jib and the adapter on which it is mounted prevents rearward tipping over of the jib and activates a safety control switch operating mechanism. The several masts, tension links, folding ladders and backstays fold compactly onto the base section of the luffing jib for easy storage and transport without separation and misarrangement of parts. A bridle storage and lifting arrangement is also disclosed.

We claim: 
     
       1. In a crane, a main boom having a top wall with an adjacent side wall, bracket means carried by one side of said boom, a bridle carriage means pivotally connected to the bracket means by a pivot means defining a pivot axis parallel with the longitudinal axis of said boom and having a lockable and releasable linear movement carriage element, means to releasably lock a bridle assembly to said carriage element, power means to arcuately swing the bridle carriage means from a position adjacent one side of the boom to a position substantially parallel with the adjacent top wall of the boom wherein the carriage element has its axis disposed across the top wall of said boom, whereby the carriage element upon release is shiftable on a linear path with the bridle assembly to a bridle assembly deployment and retrieval position adjacent to the top wall of the boom. 
     
     
       2. In a crane, a main boom having a top wall with an adjacent side wall, bracket means carried by one side of said boom, a bridle carriage means pivotally connected to the bracket means and having a lockable and releasable linear movement carriage element, means to releasably lock a bridle assembly to said carriage element, power means to swing the bridle carriage means to a position where the carriage element has its axis disposed across the top wall of said boom, whereby the carriage element upon release is shiftable on a linear path with the bridle assembly to a bridle assembly deployment and retrieval position adjacent to the top wall of the boom, and a stabilizing support element carried by said boom for a cantilevered end portion of the carriage element in the last-named position of the carriage element on said boom. 
     
     
       3. In a crane, a main boom having a top wall with an adjacent side wall, bracket means carried by one side of said boom, a bridle carriage means pivotally connected to the bracket means and having a lockable and releasable linear movement carriage element, means to releasably lock a bridle assembly to said carriage element, a stabilizing support element carried by said one side of said boom for a cantilevered end portion of the carriage element when the latter is stored at the one side of the boom, power means to swing the bridle carriage means to a position wherein the carriage element has its axis disposed across the top wall of said boom, whereby the carriage element upon release is shiftable on a linear path with the bridle assembly to a bridle assembly deployment and retrieval position adjacent to the top wall of the boom. 
     
     
       4. In a crane as defined in claim 3, and said power means comprising a cylinder unit coupled between the stabilizing support element and bridle carriage means. 
     
     
       5. In a crane, a main boom having a top wall with an adjacent side wall, bracket means carried by one side of said boom, a bridle carriage means pivotally connected to the bracket means and having a lockable and releasable linear movement carriage element, a pair of spaced posts on said carriage element and projecting beyond one side thereof, fastener means coacting with said posts to releasably lock the triangular frame of a bridle assembly to said carriage element, power means to swing the bridle carriage means to a position wherein the carriage element has its axis disposed across the top wall of said boom, whereby the carriage element upon release is shiftable on a linear path with the triangular frame bridle assembly to a bridle assembly deployment and retrieval position adjacent to the top wall of the boom. 
     
     
       6. In a crane as defined in claim 5, and said carriage element comprising a straight bar-like element, the bridle carriage means including a roller guide unit for the bar-like element pivoted to the bracket means. 
     
     
       7. In a crane as defined in claim 5, in which said fastener means are threaded fastener means, locator means on said posts for the opposite sides of the triangular frame bridle assembly, and said posts, threaded fastener means and locator means positioned on opposite sides of the triangular frame bridle assembly. 
     
     
       8. In a crane, a main boom having a top wall with an adjacent side wall, bracket means carried by one side of said boom, a bridle carriage means pivotally connected to the bracket means, said bridle carriage means having a lockable and releasable linear movement carriage element and having a roller guide unit for the carriage element pivotally connected to the bracket means, means to releasably lock a bridle assembly to said carriage element, power means to swing the bridle carriage means to a position wherein the carriage element has its axis disposed across the top wall of said boom, whereby the carriage element upon release is shiftable on a linear path with the bridle assembly to a bridle assembly deployment and retrieval position adjacent to the top wall of the boom. 
     
     
       9. In a crane as defined in claim 8, and the carriage element comprising a substantially rectangular cross section elongated bar-like element, and said roller guide unit including spaced pairs of guide rollers engaging opposite walls of the bar-like element.